One of the many riddling titles that Bilbo Baggins invented to hide his identity from the DragonSmaug. It was a reference to his adventures in Mirkwood, where he had used his short Elvish sword to rescue his Dwarf companions from monstrous spiders. (Bilbo cast himself as the fly the spiders attempted to catch, only to find that it carried a deadly sting.) Before that time, Bilbo's sword had been unnamed, but after the killing of a giant spider he gave it a fitting name: 'Sting'.